列添加到現有的表我想一列添加到現有表，其價值依賴於其他的列存儲其值取決於其他列

Question

。 STORE有兩個值，T或D.如果存儲值是T，那麼我希望添加的列中的值爲1，否則爲零。有什麼辦法嗎？

Answer 1

Oracle不支持此在創建或更改表的命令。

相反，使用：

ALTER TABLE your_table ADD c INTEGER; 

UPDATE your_table SET c = CASE WHEN store = 'T' THEN 1 ELSE 0 END; 

Answer 2

視圖可以是一種解決方案：

create view v_your_table as 
select your_table.*, case when STORE = 'T' than 0 else 1 end as comp from your_table; 

Answer 3

一個虛擬列可以做到在11g：

SQL> create table yourtab (store varchar2(1)); 

Table created. 

SQL> alter table yourtab add col as (case store when 'T' then 1 else 0 end); 

Table altered. 

SQL> insert into yourtab (store) values ('T'); 

1 row created. 

SQL> insert into yourtab (store) values ('D'); 

1 row created. 

SQL> select * from yourtab; 

S  COL 
- ---------- 
T   1 
D   0 

或觸發方法，如果你對10g或之前：它給

SQL> create table yourtab (store varchar2(1), col number); 

Table created. 

SQL> create trigger yourtab_biu 
    2 before insert or update on yourtab 
    3 for each row 
    4 declare 
    5 begin 
    6 :new.col := case :new.store when 'T' then 1 else 0 end; 
    7 end; 
    8/

Trigger created. 

SQL> insert into yourtab (store) values ('T'); 

1 row created. 

SQL> insert into yourtab (store) values ('D'); 

1 row created. 

SQL> select * from yourtab; 

S  COL 
- ---------- 
T   1 
D   0